The thermal conductivity of $KH_2PO_4$ single crystal was measured in the temperature range from 110˚K to 240˚K. The thermal conductivity along a-axis was compared with that of c-axis. The conductivity decreases gradually with falling temperature in the para electric state and it rises steeply just below the Curie temperature 122˚K. There is little difference between the thermal conductivity along a-axis and that along c-axis in the para electric region. However a small anisotropy was found in the steeply increasing region of the ferroelectric phase. This is thought to be related to the hydrogen bonds which lie in the plane normal to the c-axis.
